Hobbs
threading of plastic pipe



DEFENSIVE PUBLICATION UNITED STATES PATENT OFFICE Published at therequest of the applicant or owner in accordance with the Notice of Dec.16, 1969, 869 0.G. 687. The abstracts of Defensive Publicationapplications are identified by distinctly numbered series and arearranged chronologically. The heading of each abstract indicates thenumber of pages of specification. including claims and sheets ofdrawings contained in the application as originally filed. The files ofthese applications are available to the public for inspection andreproduction may be purchased for 30 cents a sheet.

Defensive Publication applications have not been examined as to themerits of alleged invention. The Patent Otfice makes no assertion as tothe novelty of the disclosed subject matter.

PUBLISHED JUNE 9, 1970 Threading polyethylene pipe to avoid reducing itsdiameter is accomplished by heating the end portion of the pipe on whichthreads are to be placed to the softening point and then forcing thesoftened portion completely into a closed-end cylindrical mold providedwith internal threads of the desired depth, pitch and length. The moldis also provided with an internally disposed mandrel of approximatelythe same internal diameter of the pipe and rigidly attached to theclosed end thereof, providing means whereby the softened plastic of thepipe structure will completely fill the threads of the mold along thelength of the mandrel. Upon cooling, the thus threaded pipe can beunscrewed from the mold end and will have the desired threads externallydisposed thereon Without reduction of the diameter of the pipe andwithout reduction in its original pressure rating as determined bystandard pressure rating tests,

June 9, 1970 H. K. HOBBS THREADING OF PLASTIC PIPE Filed Dec. 12, 1969FIG.I

HOWARD H. HOBBS INVENTOR.

FIG.'3

ATTORNEY

